Metal-insulator-metal (MIM) capacitors are utilized in many circuit applications including DRAM cells for memory storage, microprocessors for decoupling capacitance, RF circuits for oscillators, phase-shift networks, and coupling and bypass, as well as mixed-signal devices for decoupling and high-frequency noise filters.
Capacitors have historically produced by depositing a layer of insulating material over a bottom metal plate and then depositing a top metal plate over the insulating material layer and parallel to the bottom metal plate. The capacitance of such structures is a function of several variables, such as the surface area of the two parallel plates, the spacing between the plates, and the dielectric constant of the insulating material used. As with other circuit components, there is a constant demand for more efficient capacitors. While the capacitance of a MIM capacitor can be increased by expanding the size or surface area of the metal plates, this also consumes more space. Thus, it is particularly desirable to increase the capacitance of a MIM capacitor per unit area of substrate used, such that a significantly increased capacitance can be achieved with little or no increase in surface area. Thus, there is a need for providing higher efficiency and/or performance MIM capacitor structures. It would also be desirable if such structures were compatible with standard semiconductor processing techniques.